Change search
ReferencesLink to record
Permanent link

Direct link
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.ORCID iD: 0000-0002-9769-8016
2011 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 732, no 1, 49- p.Article in journal (Refereed) Published
Abstract [en]

We consider the emission of photons from the inner parts of a relativistically expanding plasma outflow, characterized by a constant Lorentz factor, Gamma. Photons that are injected in regions of high optical depth are advected with the flow until they escape at the photosphere. Due to multiple scattering below the photosphere, the locally emerging comoving photon distribution is thermal. However, as an observer simultaneously sees photons emitted from different angles, hence with different Doppler boosting, the observed spectrum is a multicolor blackbody. We calculate here the properties of the observed spectrum at different observed times. Due to the strong dependence of the photospheric radius on the angle to the line of sight, for parameters characterizing gamma-ray bursts (GRBs) thermal photons are seen up to tens of seconds following the termination of the inner engine. At late times, following the inner engine termination, both the number flux and energy flux of the thermal spectrum decay as F proportional to t(-2). At these times, the multicolor blackbody emission results in a power law at low energies (below the thermal peak), with power-law index F-nu proportional to nu(0). We discuss the implications and limitations of this result in the study of GRBs.

Place, publisher, year, edition, pages
2011. Vol. 732, no 1, 49- p.
Keyword [en]
gamma rays, general, plasmas, radiation mechanisms, thermal, radiative transfer, scattering, X-rays: bursts
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-33247DOI: 10.1088/0004-637X/732/1/49ISI: 000289626500049ScopusID: 2-s2.0-79955615545OAI: diva2:415236
QC 20110506Available from: 2011-05-06 Created: 2011-05-02 Last updated: 2011-05-06Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Ryde, Felix
By organisation
Particle and Astroparticle Physics
In the same journal
Astrophysical Journal
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 29 hits
ReferencesLink to record
Permanent link

Direct link